PHYLUM CHORDATA 



535 



and strong, with five digits in each foot. The upper surface 

 of the head and body, the sides of the latter, and the entire 

 surface of the tail are covered with an investment of rounded 

 horny epidermal scales. The lower surface is covered with 

 hair, and there are a few coarse hairs between the scales. 

 There are five digits in both manus and pes. 



The aard-varks (Fig. 323) have a thick-set body, the head 

 produced into a long muzzle with a small tubular mouth, the 

 pinnae of great length, the tail long and thick. The fore- 

 limbs are short and stout, with four toes. The hind-limb 



Fig 324. — Killer (Orca gladiator) . (After True.) 



is five-toed. The surface is covered with thick skin with 

 sparse hairs. 



The Cetacea (Fig. 324), among which are the largest of 

 existing mammals, are characterised by the possession of a 

 fusiform fish-like body, tapering backwards to the tail, which 

 is provided with a horizontally expanded caudal fin divided 

 into two lobes or " flukes," and a relatively large head, not 

 separated from the body by any distinct neck. A dorsal 



